Dosing systems for septic fields have been suggested in the past, generally involving the use of siphons or pumps. However, pumps are a potential source of trouble and consume energy. They are expensive and complex to install and should be used only when the disposal field is at a higher elevation than the outlet of the septic tank. Siphons are simple and rely on gravity to operate but they are also disadvantageous. Because of their downward projecting trap, siphons are difficult to incorporate into a precast concrete structure and require extensive work to install in the field. Siphons rely upon a small diameter vent tube to operate, which is prone to clog, rendering the siphon inoperable. They also waste elevation to achieve sufficient "draw down" which can be a problem in installations with minimal elevation changes.
In U.S. Pat. No. 4,439,323, Ball proposes a pump-driven septic system which provides dosing of effluent into a septic field. However, as discussed above, the use of a pump has disadvantages, due to breakdown and energy consumption. Accordingly, pumps should only be incorporated where the disposal field is at a higher elevation than the outlet of the septic tank, which requires the energy needed to pump the effluent "up hill".
In U.S. Pat. No. 4,838,731, Gavin proposes a dosing "box" for a septic system having a pivoting tray with a counterweight. The tray is filled with effluent as it enters the tank and when the weight of effluent in the tray overcomes the counterweight, the tray tips and spills its contents to the septic tank outlet. Once emptied, the tray then returns to its upright position. The use of such a tray, however, can be undesirable because of its limited size. In fact, Gavin specifies that the tray of his invention is 2.3 gallons in volume. This is a significant limitation since the flow of effluent into the septic tank is not completely uniform and the tray of Gavin can easily be overwhelmed by the inflow of effluent.